Laryngotracheitis infection

FACTS OF INFECTIOUS LARYNGOTRACHEITIS (LT) IN CHICKENS

• It’s a highly infectious disease of worldwide distribution.
• It induces significant economic losses due to high morbidity and variable mortality, drop in egg production, weight loss and susceptibility to other respiratory infections.
• The disease is caused by a Herpes viral infection characterized by latency, persistency and reversion to virulence.
• The viral infection induces chronic carrier for life, allowing the transmission to other birds and environmental contamination.

THE DIAGNOSIS CAN BE DONE BY

Clinical signs (Figure 1) Post-mortem lesions: they may vary from mild to severe (Figure 2) Histopathology: observations of typical giant cells and intranuclear inclusion bodies in the tracheal epithelium in the early stage of infection Virus isolation Molecular biology methods to detect viral DNA such as PCR Serology Other diagnostic methods such as immunohistochemistry and immunofluorescence

Figure 1: suffocation Figure 1: suffocation Figure 2: severe laringotracheitis Figure 2: severe laringotracheitis

CURRENT LIVE LT (CEO: CHICKEN EMBRYO ORIGIN OR TCO: TISSUE CULTURE ORIGIN) VACCINES SITUATION

These vaccines are able to provide protection but conversely, they have many side effects (Bagust 1986 and 1995, Graham 2000):

• Latent and persistent LT virus infection = chronic carrier state in vaccinated birds
• Reversion to virulence
• Transmission to other birds
• Shed into the environment
• Induce vaccine reactions that affect growth performance